Within living memory, this simple dish was a staple on meat-and-three menus throughout the rural South. Juice from the vegetables stirred with oil and vinegar make a mild, flavorful vinaigrette best with beans or cold meats. I love to use it in the old three-bean-salad, and it’s great with fish or shellfish.
Use fresh vegetables; supermarket tomatoes don’t have enough of that wonderful gelatin surrounding the seeds, and those cucumbers are too watery. Sweet yellow onions spoil the bite, and red onions discolor the mix; white boilers are best. Cut vegetables into bite-sized pieces, place in a glass or ceramic bowl and toss with a generous salting and a good bit of fresh ground black pepper.
Resist the temptation to use garlic and/or herbs. Add enough white vinegar to cover the vegetables by half and half that amount of corn oil. Do not use olive oil, which will coagulate when refrigerated. Refresh the mix with vegetables, seasonings, and liquids as needed.